“…This behavior could be associated to stress concentration effect and the lower stiffness of the laminates due to the presence of the holes. Similar observations were reported by Santos et al 30 for composite laminates after to analyze the effect of distance between impact point and hole position.Figure 7.Ultrasonic C-scan images of the impact side of composite plates tested at 10 J impact energy.Figure 8.Ultrasonic C-scan images of the impact side of composite plates tested at 15 J impact energy.…”
Section: Resultssupporting
confidence: 80%
“…This behavior could be associated to stress concentration effect and the lower stiffness of the laminates due to the presence of the holes. Similar observations were reported by Santos et al 30 for composite laminates after to analyze the effect of distance between impact point and hole position.…”
Section: Evaluation Of Impact Damagesupporting
confidence: 87%
“…In the case of 10 J (Figure 4(a)), D-GFRP specimen shows a greater peak force during impact compared to those D-GFRP-DH12 and D-GFRP-DH18, indicating that the presence of drilled holes tends to reduce the impact response of composite laminates because of the holes affect considerably the stiffness of the specimen. 30 A similar trend was observed for wet specimens where the peak force of W-GFRP is higher compared with W-GFRP-DH12 and W-GFRP-DH18. Furthermore, the D-GFRP-DH12 and W-GFRP-DH12 specimens show lower peak force comparing with the D-GFRP-DH18 and W-GFRP-DH18 samples meaning that the distance of drilled holes to the impact point play a paramount role on the impact behavior of composite laminates.…”
During their service life, composite marine structures made up of glass fiber reinforced polymers are susceptible to be affected by environmental and loading conditions such as seawater and low velocity impacts which can cause them severe structural damage. Based on this fact and concern, the present work investigates the influence of seawater aging on impact behavior of glass fiber/epoxy composite laminates with and without drilled holes. To achieve this goal, glass fiber/epoxy laminates were manufactured by resin transfer molding and then cut into specimens for low velocity impact testing. Before impact tests, specimens were immersed in artificial seawater at 70°C for 1464 h. After that time, dry (before seawater aging) and wet (after seawater aging) specimens were tested at 10 and 15 J impact energies using a drop-weight impact tower. The results of accelerated seawater aging confirmed that the presence of drilled holes in composites does not influence on their moisture absorption content and diffusion coefficient. The impact test results showed that the impact properties of wet specimens are significantly lower respect to dry specimens. It was found that the peak force of wet specimens displays a reduction of approximately 40% with respect to the dry specimens as a consequence of moisture absorption which causes plasticization of the polymeric matrix. Ultrasonic C-scan inspection showed that damage area of wet specimen increased up to 250% compared to that of dry specimen. Fractographic analyses by scanning electron microscopy and X-ray computerized tomography revealed that low velocity impact in composite laminates produced damage mechanisms associated to matrix cracking, fiber/matrix debonding, fiber breakage, and delamination, which were more prominent in laminates with drilled holes and subjected to a previous seawater exposition.
“…This behavior could be associated to stress concentration effect and the lower stiffness of the laminates due to the presence of the holes. Similar observations were reported by Santos et al 30 for composite laminates after to analyze the effect of distance between impact point and hole position.Figure 7.Ultrasonic C-scan images of the impact side of composite plates tested at 10 J impact energy.Figure 8.Ultrasonic C-scan images of the impact side of composite plates tested at 15 J impact energy.…”
Section: Resultssupporting
confidence: 80%
“…This behavior could be associated to stress concentration effect and the lower stiffness of the laminates due to the presence of the holes. Similar observations were reported by Santos et al 30 for composite laminates after to analyze the effect of distance between impact point and hole position.…”
Section: Evaluation Of Impact Damagesupporting
confidence: 87%
“…In the case of 10 J (Figure 4(a)), D-GFRP specimen shows a greater peak force during impact compared to those D-GFRP-DH12 and D-GFRP-DH18, indicating that the presence of drilled holes tends to reduce the impact response of composite laminates because of the holes affect considerably the stiffness of the specimen. 30 A similar trend was observed for wet specimens where the peak force of W-GFRP is higher compared with W-GFRP-DH12 and W-GFRP-DH18. Furthermore, the D-GFRP-DH12 and W-GFRP-DH12 specimens show lower peak force comparing with the D-GFRP-DH18 and W-GFRP-DH18 samples meaning that the distance of drilled holes to the impact point play a paramount role on the impact behavior of composite laminates.…”
During their service life, composite marine structures made up of glass fiber reinforced polymers are susceptible to be affected by environmental and loading conditions such as seawater and low velocity impacts which can cause them severe structural damage. Based on this fact and concern, the present work investigates the influence of seawater aging on impact behavior of glass fiber/epoxy composite laminates with and without drilled holes. To achieve this goal, glass fiber/epoxy laminates were manufactured by resin transfer molding and then cut into specimens for low velocity impact testing. Before impact tests, specimens were immersed in artificial seawater at 70°C for 1464 h. After that time, dry (before seawater aging) and wet (after seawater aging) specimens were tested at 10 and 15 J impact energies using a drop-weight impact tower. The results of accelerated seawater aging confirmed that the presence of drilled holes in composites does not influence on their moisture absorption content and diffusion coefficient. The impact test results showed that the impact properties of wet specimens are significantly lower respect to dry specimens. It was found that the peak force of wet specimens displays a reduction of approximately 40% with respect to the dry specimens as a consequence of moisture absorption which causes plasticization of the polymeric matrix. Ultrasonic C-scan inspection showed that damage area of wet specimen increased up to 250% compared to that of dry specimen. Fractographic analyses by scanning electron microscopy and X-ray computerized tomography revealed that low velocity impact in composite laminates produced damage mechanisms associated to matrix cracking, fiber/matrix debonding, fiber breakage, and delamination, which were more prominent in laminates with drilled holes and subjected to a previous seawater exposition.
“…Whether the distinction between the relevant sources of damage that is more harmful to each type of material is correct or not, it is expected that the exposure to operating conditions and external factors promotes the initiation, accumulation and propagation of damage [6]. This has led researchers to perform an extensive research on the influence of different load cases and external conditions on the damage tolerance of composite materials, such as: the influence of fabric architecture and resin toughness on the impact resistance ( [69,82,93,100,101,192,215,250,280] and [18-20, 100, 101, 115, 137, 209, 228, 243, 250], respectively) and damage tolerance ( [40,46,91,100,101,185] and [35,86,190,227,228,254], respectively) of CFRP, the effect of fracture toughness [1,82,115,136,222,240,241,243,280], repeated impact [15,17,107,117,210,211], impact geometry [8,16,27,34,76,…”
“…Furthermore, at higher applied stresses, the cracks also emanated from the free edges. Santos et al [33] evaluated the low-velocity impact response of holed GFRP laminates. They observed that there was a significant influence on fatigue life in notched samples compared to the control samples.…”
This paper studies the effect of seawater immersion on the fatigue behavior of notched carbon/epoxy laminates. Rectangular cross-section specimens with a central hole were immersed in natural and artificial seawater for different immersion times (0, 30 and 60 days), being the water absorption rate evaluated over time. After that, fatigue tests were performed under uniaxial cyclic loading using a stress ratio equal to 0.1. After the tests, the optical microscopy technique allowed the examination of the failure micro-mechanisms at the fracture surfaces. The results showed that saturation appeared before 30 days of immersion and that water absorption rates were similar for natural and artificial seawater. The S–N curves showed that the seawater immersion affects the fatigue strength, but there were no relevant effects associated with the type of seawater. Moreover, it was also clear that fatigue life was similar for long lives, close to 1 million cycles, regardless of the immersion time or the type of seawater. On the contrary, for short lives, near 10 thousand cycles, the stress amplitude of dry laminates was 1.2 higher than those immersed in seawater. The failure mechanisms were similar for all conditions, evidencing the fracture of axially aligned fibres and longitudinal delamination between layers.
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